Revealing Degas’s process and material choices in a late pastel on tracing paper with visible-to-near-infrared reflectance imaging spectroscopy

Abstract

ABSTRACT Visible-to-near-infrared reflectance imaging spectroscopy (417–2500 nm), the collection of hundreds of images in contiguous narrow spectral bands calibrated to reflectance, was employed to characterize drawing materials in Ballet Scene, a large-scale pastel on tracing paper by Edgar Degas. The spectral range from 417 to 950 nm proved useful in identifying and mapping the complex pigment application. The near-infrared (NIR) range from 962 to 2500 nm allowed visualization of underdrawing below multiple layers of pastel and fixative that depict positions of the dancers’ bodies and costumes in the pastel’s early developmental stages. This study compares the visualization of underdrawing in images gathered from reflectance imaging spectroscopy in narrow spectral bands with those obtained from infrared reflectography (IRR) in broad spectral bands, a technique widely used in the art conservation field. Passages in which Degas explores various limb positions are better visualized with image products derived from reflectance imaging spectroscopy than broadband IRR images. For example, false-color reflectance images that display narrow NIR spectral bands were useful to separate and visualize the distribution of materials and more clearly convey Degas’s processes of compositional refinement. These results provide a deeper understanding of Degas’s working method and explore the relationship of Ballet Scene with similar works.